Fix a crash with variably-modified parameter types in a naked function

Naked functions have no prolog, so it's not valid to emit prolog code
to evaluate the variably-modified type. This fixes Issue 50541.

1 files changed, 15 insertions, 16 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index de71743..15719d1 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -1195,27 +1195,26 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
   }
 
   // If any of the arguments have a variably modified type, make sure to
-  // emit the type size.
-  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
-       i != e; ++i) {
-    const VarDecl *VD = *i;
-
-    // Dig out the type as written from ParmVarDecls; it's unclear whether
-    // the standard (C99 6.9.1p10) requires this, but we're following the
-    // precedent set by gcc.
-    QualType Ty;
-    if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD))
-      Ty = PVD->getOriginalType();
-    else
-      Ty = VD->getType();
+  // emit the type size, but only if the function is not naked. Naked functions
+  // have no prolog to run this evaluation.
+  if (!FD || !FD->hasAttr<NakedAttr>()) {
+    for (const VarDecl *VD : Args) {
+      // Dig out the type as written from ParmVarDecls; it's unclear whether
+      // the standard (C99 6.9.1p10) requires this, but we're following the
+      // precedent set by gcc.
+      QualType Ty;
+      if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD))
+        Ty = PVD->getOriginalType();
+      else
+        Ty = VD->getType();
 
-    if (Ty->isVariablyModifiedType())
-      EmitVariablyModifiedType(Ty);
+      if (Ty->isVariablyModifiedType())
+        EmitVariablyModifiedType(Ty);
+    }
   }
   // Emit a location at the end of the prologue.
   if (CGDebugInfo *DI = getDebugInfo())
     DI->EmitLocation(Builder, StartLoc);
-
   // TODO: Do we need to handle this in two places like we do with
   // target-features/target-cpu?
   if (CurFuncDecl)